Re: [Python-Dev] Terminology for PEP 343
On Sun, Jul 03, 2005, Nick Coghlan wrote: [...] Anyway, I stuck with 'exit' for this - I prefer slightly awkard phrasing in the explanation to awkwardness in the pairing of the names. [...] __exit__(exc_type, exc_value, exc_traceback): Called as execution exits the contained suite. If the suite was exited due to an exception, the details of that exception are passed as arguments. Otherwise, all three arguments are set to None. My take is that the primary awkwardness results from all the ex: execution, exits, exception. If we care, I guess leave is okay. Nice work! -- Aahz ([EMAIL PROTECTED]) * http://www.pythoncraft.com/ f u cn rd ths, u cn gt a gd jb n nx prgrmmng. ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
Nick Coghlan wrote: On the other hand 'enter and exit' rolls off the tongue significantly better than 'enter and leave' My only concern is enter and exit may be too general. They are frequently used in other places, although __enter__ and __exit__ are less common, so maybe it's a non issue. The terms __begin__ and __end__, are nearly as general, but they stress better that there are three parts, a beginning, middle and ending. All of which just leads me to the conclusion that English is a screwy language, and I already knew that ;) I nowe that tue, but fixxing it issint backward compattibbal. ;-) Anyway, I stuck with 'exit' for this - I prefer slightly awkard phrasing in the explanation to awkwardness in the pairing of the names. After reading Michael Hudsun's post: I used a with statement to establish and dis-establish an error handler -- would you call that a resource? He has a good point, maybe we are confusing what a with-block does, with how it can be used. So something along the lines of ... With-Mangager Blocks A With-Manager Block is used to combine related initiation and finalization routines from a Manager object with a local block of code. Python will attempt to execute the finalization routine even if an error occurs which makes With-Manager Blocks useful for writing algorithms which require dependable closure or release of an acquired resource after the code block is executed. etc... That's a nice start on the docs Nick. Cheers, Ron ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
How about simply with block or guarded scope or something like that? Michael On 7/3/05, Ron Adam [EMAIL PROTECTED] wrote: Nick Coghlan wrote: On the other hand 'enter and exit' rolls off the tongue significantly better than 'enter and leave' My only concern is enter and exit may be too general. They are frequently used in other places, although __enter__ and __exit__ are less common, so maybe it's a non issue. The terms __begin__ and __end__, are nearly as general, but they stress better that there are three parts, a beginning, middle and ending. All of which just leads me to the conclusion that English is a screwy language, and I already knew that ;) I nowe that tue, but fixxing it issint backward compattibbal. ;-) Anyway, I stuck with 'exit' for this - I prefer slightly awkard phrasing in the explanation to awkwardness in the pairing of the names. After reading Michael Hudsun's post: I used a with statement to establish and dis-establish an error handler -- would you call that a resource? He has a good point, maybe we are confusing what a with-block does, with how it can be used. So something along the lines of ... With-Mangager Blocks A With-Manager Block is used to combine related initiation and finalization routines from a Manager object with a local block of code. Python will attempt to execute the finalization routine even if an error occurs which makes With-Manager Blocks useful for writing algorithms which require dependable closure or release of an acquired resource after the code block is executed. etc... That's a nice start on the docs Nick. Cheers, Ron ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/michael.walter%40gmail.com ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Adding the 'path' module (was Re: Some RFE for review)
On 6/30/05, Neil Hodgson [EMAIL PROTECTED] wrote: One benefit I see for the path module is that it makes it easier to write code that behaves correctly with unicode paths on Windows. Currently, to implement code that may see unicode paths, you must first understand that unicode paths may be an issue, then write conditional code that uses either a string or unicode string to hold paths whenever a new path is created. Then maybe the code that handles Unicode paths in arguments should be fixed rather than adding a module that encapsulates a work-around... -- --Guido van Rossum (home page: http://www.python.org/~guido/) ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
[Michael Walter] How about simply with block or guarded scope or something like that? How would you use that to describe decimal.Context() objects after Nick adds the __enter__ and __exit__ magic methods? We want something as direct as, xrange objects are iterable. Raymond ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
[Ron Adam] The terms __begin__ and __end__, are nearly as general, but they stress better that there are three parts, a beginning, middle and ending. -1 Those are too generic to communicate anything. You would be better off using beginwith and endwith or somesuch. Raymond ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
Michael Hudson [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] Thing is, there may be no resource; in my talk at EuroPython: http://starship.python.net/crew/mwh/recexc.pdf I used a with statement to establish and dis-establish an error handler -- would you call that a resource? Yes -- now that you suggested it, given what you had on your slides ;-) An emergency backup resource is different from a normal production resource (opened file for instance), but I can still see it as a resource. Terry J. Reedy ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
On 3 Jul 2005, at 18:25, Josiah Carlson wrote: Just because not all cars are used as vehicles, does that mean that cars are not vehicles? No, but it means calling all vehicles cars is dumb. There may be cases where the object being managed is not a resource per-se, but that doesn't mean that the mechanism is misnamed as a 'resource manager'; it's just the most common use case that any of us have managed to think of (as of yet). This is possible. I just wanted to expand everyone's minds :) Cheers, mwh ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
There may be cases where the object being managed is not a resource per-se, but that doesn't mean that the mechanism is misnamed as a 'resource manager'; it's just the most common use case that any of us have managed to think of (as of yet). [Michael Hudson] This is possible. I just wanted to expand everyone's minds :) Stick by your guns. The mechanism is more general than resource management. Like decorators, the encapsulation of a try/finally wrapper is completely generic and not married to the resource management context. Raymond ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
On Sun, Jul 03, 2005, Raymond Hettinger wrote: [Michael Walter] How about simply with block or guarded scope or something like that? How would you use that to describe decimal.Context() objects after Nick adds the __enter__ and __exit__ magic methods? We want something as direct as, xrange objects are iterable. How about decimal.Context() objects are managed resources or ...have guarded scopes? (I'm not terribly wild about either, but they are fairly simple and direct.) -- Aahz ([EMAIL PROTECTED]) * http://www.pythoncraft.com/ f u cn rd ths, u cn gt a gd jb n nx prgrmmng. ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
Hmm: Guarding a scope with a decimal.Context() object explain effect. What do you think? (I'm not sure myself, but we even got a with in there :-) Michael On 7/3/05, Raymond Hettinger [EMAIL PROTECTED] wrote: [Michael Walter] How about simply with block or guarded scope or something like that? How would you use that to describe decimal.Context() objects after Nick adds the __enter__ and __exit__ magic methods? We want something as direct as, xrange objects are iterable. Raymond ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
At 03:04 PM 7/3/2005 +0100, Michael Hudson wrote: Phillip J. Eby [EMAIL PROTECTED] writes: At 05:41 PM 6/30/2005 -0400, Raymond Hettinger wrote: With 343 accepted, we can now add __enter__() and __exit__() methods to objects. What term should describe those objects in the documentation? Resource managers. Thing is, there may be no resource; in my talk at EuroPython: http://starship.python.net/crew/mwh/recexc.pdf I used a with statement to establish and dis-establish an error handler -- would you call that a resource? Yes; an error handling resource is no different than say, a decimal context resource in this respect. A with statement defines the scope of use or applicability of some resource; the resource manager is the object that is notified as to when the scope is entered and exited, so that it can appropriately manage the resource. Some resources may be their own default resource manager, but it's always possible to create a different resource management policy by creating a new resource manager. I think this is a clear and straightforward explanation of what with does and what you can do with it. ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
At 03:41 PM 7/3/2005 -0400, Raymond Hettinger wrote: There may be cases where the object being managed is not a resource per-se, but that doesn't mean that the mechanism is misnamed as a 'resource manager'; it's just the most common use case that any of us have managed to think of (as of yet). [Michael Hudson] This is possible. I just wanted to expand everyone's minds :) Stick by your guns. The mechanism is more general than resource management. Like decorators, the encapsulation of a try/finally wrapper is completely generic and not married to the resource management context. Expand your mind. :) Resource can include whatever objects you want it to -- or no objects at all. A resource can be conceptual - like for example the user's attention, or the contents of a status bar or log message, or the timing/profiling of an activity. I think maybe you're projecting one particular concept of resource management (acquisition/release) and therefore say it's too narrow. But that's like I'm saying vehicle, and you think that means car. Should we give mind-expanding examples of resource? Yes, sure. But it's easier to say and teach resource management first, and then expand the concept, than to start with some more nebulous concept and then say, but mostly you're going to use it to manage resources of various kinds. :) If you did want to start with something vague, you could always call it context management, and call the objects context listeners, saying that the with statement defines a context in which its body occurs, and the context listener is notified of the context's entry and exit. But I don't think that this really works as the primary explanation; I think it's better as a mind-expanding Another way to think of this is... add-on to the simple resource management explanation. ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
Hmm, I think I'm seeing mostly the (guarded) entry/exit part of guard metaphor, but I see what you mean (not allowing entry, so to say, right?). Not sure. Michael On 7/3/05, Raymond Hettinger [EMAIL PROTECTED] wrote: Guarding a scope with a decimal.Context() object explain effect. Doesn't guard suggestion conditional execution? Raymond ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
I'm referring to the specific meaning of guard in a computer science context: http://www.computer-dictionary-online.org/guard.htm?q=guard From David Gries, The Science of Programming, if statement contains two entities of the form B -- S wehere B is a Boolean expression and S a command. B -- S is called a guarded command. I believe that terminology is rooted in Dijkstra's language of guarded commands (used to express and facilitate program proofs). They are essentially the same as conditionally executed statements but may be executed non-deterministically: http://cs-exhibitions.uni-klu.ac.at/contentGuardedCommand.php Also, I believe the pattern matching part of Prolog clauses are called guards; however, the conditional execution is deterministic (the first match is the one that fires) and potentially recursive. This terminology is used consistently among various functional programming languages. From, http://www.cs.ecu.edu/~karl/astarte/glossary.html , A guard in a case is the condition that is being tested. For example, in case a = b, expression a is the guard. In predicate calculus, the phrase, strengthening the guard has a specific meaning with the guard part being consistent with the above. One example: http://www.cs.utexas.edu/users/psp/unity/notes/07-89.pdf IOW, guard is a specific term, not an amorphous metaphor that can be accurately applied to the enter/exit or enter/leave pair. Raymond -Original Message- From: Michael Walter [mailto:[EMAIL PROTECTED] Sent: Sunday, July 03, 2005 10:28 PM To: Raymond Hettinger Cc: [EMAIL PROTECTED]; python-dev@python.org Subject: Re: [Python-Dev] Terminology for PEP 343 Hmm, I think I'm seeing mostly the (guarded) entry/exit part of guard metaphor, but I see what you mean (not allowing entry, so to say, right?). Not sure. Michael On 7/3/05, Raymond Hettinger [EMAIL PROTECTED] wrote: Guarding a scope with a decimal.Context() object explain effect. Doesn't guard suggestion conditional execution? Raymond ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
The mechanism is more general than resource management. Like decorators, the encapsulation of a try/finally wrapper is completely generic and not married to the resource management context. [Phillip] Expand your mind. :) Resource can include whatever objects you want it to -- or no objects at all. There is no value in expanding a concept to the point of being meaningless (i.e. meaning whatever you want it to or nothing at all). Instead, we need a phrase that expresses the essence of the following: abc = EXPR exc = (None, None, None) VAR = abc.__enter__() try: try: BLOCK except: exc = sys.exc_info() raise finally: abc.__exit__(*exc) There is nothing in that that says resource managed. The pre/post steps could do almost anything from logging, to changing environments, to translating, launching/joining unrelated threads, to communicating with other processes, etc. Ideally, the phrase needs to fit in a list of all of the other properties of the abc object (i.e. abc objects are callable, iterable, support the buffer interface, and are withable or somesuch). Another trouble with resource managed is that it makes little sense even when describing something that is clearly a resource (for instance, locking objects are resource managed, what the heck could that mean, there is no hint about the presence of __enter__ and __exit__ or the ability to work with the with keyword). The phrase does nothing but suggest a particular application that historically has been implemented without the new mechanism. Of course, what makes this exercise hard is that our two new keywords are prepositions and the process that they apply to is somewhat abstract. Raymond P.S. I would still like to encourage the adoption of __leave__ instead of __exit__. The first suggests part of an enter/leave pair. The latter could too easily be taken as a standalone. If everyone doesn't see the subtle reasons why __leave__ is better, then at least consider __beginwith__ and __endwith__ which say exactly what they mean and are obviously paired with each other and with the new keyword. Remember, these methods are going to show up in objects such as Context which are not primarily about 343. All of the other methods names will have nothing to do with 343, so our choice of magic names needs to be really good (as there will likely be NO contextual hints). ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Terminology for PEP 343
Oh, I remember. Agreed, it is most probably a bad choice then. One part of my brain likes: By wrapping a block in/with[*] a decimal.Context, elaborate on consequences xml.Tags used to wrap a block will print 'tag' before the block is entered, and '/tag' after execution has left. What do you think? [*] I'm not sure what's the correct English version, sorry.. if it is with, it migh be a nice way to place a hyperlink to the language reference. On 7/3/05, Raymond Hettinger [EMAIL PROTECTED] wrote: I'm referring to the specific meaning of guard in a computer science context: http://www.computer-dictionary-online.org/guard.htm?q=guard From David Gries, The Science of Programming, if statement contains two entities of the form B -- S wehere B is a Boolean expression and S a command. B -- S is called a guarded command. I believe that terminology is rooted in Dijkstra's language of guarded commands (used to express and facilitate program proofs). They are essentially the same as conditionally executed statements but may be executed non-deterministically: http://cs-exhibitions.uni-klu.ac.at/contentGuardedCommand.php Also, I believe the pattern matching part of Prolog clauses are called guards; however, the conditional execution is deterministic (the first match is the one that fires) and potentially recursive. This terminology is used consistently among various functional programming languages. From, http://www.cs.ecu.edu/~karl/astarte/glossary.html , A guard in a case is the condition that is being tested. For example, in case a = b, expression a is the guard. In predicate calculus, the phrase, strengthening the guard has a specific meaning with the guard part being consistent with the above. One example: http://www.cs.utexas.edu/users/psp/unity/notes/07-89.pdf IOW, guard is a specific term, not an amorphous metaphor that can be accurately applied to the enter/exit or enter/leave pair. Raymond -Original Message- From: Michael Walter [mailto:[EMAIL PROTECTED] Sent: Sunday, July 03, 2005 10:28 PM To: Raymond Hettinger Cc: [EMAIL PROTECTED]; python-dev@python.org Subject: Re: [Python-Dev] Terminology for PEP 343 Hmm, I think I'm seeing mostly the (guarded) entry/exit part of guard metaphor, but I see what you mean (not allowing entry, so to say, right?). Not sure. Michael On 7/3/05, Raymond Hettinger [EMAIL PROTECTED] wrote: Guarding a scope with a decimal.Context() object explain effect. Doesn't guard suggestion conditional execution? Raymond ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
